RFR: 8302871: Speed up StringLatin1.regionMatchesCI [v7]

[Martin Buchholz]

On Wed, 22 Feb 2023 07:12:35 GMT, Eirik Bjorsnos <duke at openjdk.org> wrote:

>>> Do you have an opinion on the appropriate level of documentation / comments for this kind of 'tricky' code? 
>> 
>> This code is not that tricky!  And the proposed level of documentation is excessive!  A couple of lines of explanation and perhaps a link to an external document would be good.
>> 
>> It often happens to me that I will write such exhaustive notes for myself when learning a new technology.  A year later I pare it all back because much of it is "obvious in retrospect".
>
> Thanks Martin, David, Alan.  This was instructive (and fun!)
> 
> I suggest we condense the comment to something like this:
> 
> 
> // Uppercase b1 by removing a single bit
> int upper = b1 & 0xDF;
> if (upper < 'A') {
>     return false;  // Low ASCII
> }
> ...
> 
> 
> The similar methods `toLowerCase` `toUpperCase` just above have been updated to follow the same style. (I also updated local variable names there to align better with equalsIgnoreCase)

// ASCII and Latin-1 were designed to optimize case-twiddling operations

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PR: https://git.openjdk.org/jdk/pull/12632